Go to Wages & Income > I'll choose what I work on.
At the page listing the Income topics, scroll down to Investment Income > Stocks, Crypto, Bonds, Mutual Funds, etc., Start or Update.
If you've added other financial info, scroll down to 'Add Investments'
At the next screen, you'll be able to type in your Broker Name. If you get a blank screen at this point, I'd recommend closing TurboTax, and turning off all anti-virus software and try importing again.
Make sure the program is updated from the ONLINE link at the top.
@TerryTB